FEARS that Islamist terrorists plan to hijack an Indian passenger jet and crash it into a British city helped to prompt this weekend’s heightened terror alert.

MI5 was told by the Indian authorities early last week about a suspected plot by militants linked to Al-Qaeda in Pakistan to hijack an Air India or Indian Airlines flight from Mumbai or Delhi.

The warning, which came after the capture of a suspected Islamic leader, was contained in a detailed “threat assessment” sent to MI5 by the Indian Intelligence Bureau. It did not state that Britain was a specific target. But police security sources said it had raised fears in London that a British city might be attacked.

The warning revived long-running concerns following an Al-Qaeda plot in 2003 in which a hijacked aircraft was to be flown into Heathrow airport. That incident led Tony Blair, then prime minis